This invention relates to vacuum coating installations of the type comprising an evacuable chamber and a rotatable substrate support, for the objects to be coated, arranged in the chamber. In vacuum coating installations, preferably vacuum vapor deposition installations or cathode disintegration installations, it is known how to set into rotation the holding device for the objects to be coated, this device being usually designed as a rotating basket, in order to obtain a more uniform coating. There are also known holding devices, with a central drive and with turnable support plates for the objects to be coated, and which support plates can be turned without interruption of the vacuum. This is advantageous because, with such an arrangement, objects can be placed on both sides of the support plates and the installation can thus be used more economically, or the objects, for example, lenses, which are fastened in recesses of the support plates, can be coated on both sides in one operation.
Holding and turning devices for vacuum coating installations have been disclosed in numerous patent publications, for example, in DP No. 962,488, DP No. 966,014, U.S. Pat. Nos. 2,532,971, 2,260,471, 3,396,696 and 3,643,625, DT-OS No. 1,913,318, DT-OS No. 2,209,857, DT-AS No. 2,306,173, and Oe-PS No. 199,904.
Insofar as they permit both the mentioned rotary movement and the mentioned turning of the support plates for the objects to be coated, the known systems usually comprise separate drive mechanisms for these two movements, and therefore usually include two separate, vacuum-proof, motion-transmitting bushings. Some of the known systems are very space-consuming and, because of the complications of their drives, are very prone to trouble.
The vacuum coating installation disclosed in DT-OS No. 2,306,173 avoids the mentioned disadvantage. This installation consists of an evacuable chamber, a holding device rotatable therein and having holding plates for the objects to be coated, associated means for the coating of these objects, preferably, with a vaporization or cathode disintegration system, drive means for setting the holding device into rotation about a preferably vertical axis during coating, and additional means for turning the support plates and thereby bringing them into two different coating positions. It is typical of this known installation that a drive ring, mounted for rotation about the axis of the rotatable holding device, is provided, and is so coupled with the turning mechanism of the support plates that, to each of the two directions of rotation of the drive ring, there corresponds one direction of turning of the support plates, and that additional means are provided for blocking the turning movement in the respective direction after attainment of one of the two coating positions so that, upon further rotation of the drive ring, the holding device carrying the holding plates is taken along by the drive ring in the same direction.
It has now been found that this known system is not satisfactory, inasmuch as the turning of the holding plates did not occur safely or with sufficient reliability. This difficulty appears, in particular, in coating installations in which additional heating means are provided in order to maintain the substrates at elevated temperatures during the coating, as is necessary for some coating processes. Such heating systems usually are designed as radiators arranged above the holding device for the substrates. Due to the temperature gradients then occuring in the structural elements of the system, and the resulting different thermal expansions of these parts, it may happen that a blocking of the relative movement between the drive ring, on the one hand, and the gears causing the turning of the individual holding plates, on the other hand, occurs before the turning movement is completed, that is, while the holding plates are still in an intermediate position between the two coating positions. If this occurs, the vapor deposition process must be interrupted and the vacuum chamber must be opened, often resulting in spoiling of the coating material then in the installation, or at the least, causing loss of time.
In another known coating unit disclosed in DT-OS No. 1,913,318, there is also avoided a separate movement-transmitting bushing for the turning of the holding plates, by appropriate coupling members for the actuation of more than one of the movable systems arranged in the vacuum space. This comprises a support plate, for the objects to be coated, rotatable in the interior of a vacuum bell about a vertical axis, with a mechanism which flips the support over by 180.degree. about an axis directed approximately normal to its axis of rotation, and which is arranged and designed so that the setting in motion of its operative cycles occurs through structural elements already extending into the evacuated space from the outside and used for the actuation of further functions of the overall installation. In particular, in this known installation, the flapping mechanism can be operated by means of the actuating system for the diaphragm associated with the vaporization or disintegration source.
Such a coupling between the actuation of the diaphragm and the turning of the holding plates is, however, undesirable and permissible only for specific applications, for which the machanism then must be constructed accordingly. In the known disclosure, there is mentioned an example where the turning movement is coupled with the actuating means for the diaphragm, present over a vaporization source, in such a way that, for the purpose of initiating the vapor deposition process, the diahragm can be opened without the turning mechanism going into action. However, if the diaphragm then is closed again to interrupt the vapor deposition, the turning of the holding plates through 180.degree. is effected simultaneously through a corresponding switching cam. Thus, such an arrangement permits only a single vapor coating of one plate side, and multiple coats cannot be produced therewith. In a further embodiment of this known arrangement, the flapping over can be repeated any number of times in the same vacuum, but the coupling between turning of the substrate supports and actuation of the diaphragm persists.